The effect of high temperature on reproductive biology of faba bean (Vicia faba L.)

Abstract

Higher temperatures caused by global warming have driven the need for the development of heattolerant varieties. Faba bean (Vicia faba L.) is a winter-season grain legume with a low tolerance to high temperatures, especially during the reproductive stage. There is a lack of research on faba bean heat tolerance in the northern grain crops growing region with shorter growing seasons and higher temperatures. This study aimed to better understand how heat stress affects the reproductive physiology of faba bean using diverse germplasms.48 lines were evaluated in the field at the Plant Breeding Institute of the University of Sydney at Narrabri for two years (2015-2016). Heat-tolerant genotypes were identified through the three different sowing dates with three replications. PBA Ayla was identified as a heat-tolerant genotype, and it was selected for further studies in the control environment. The same 48 genotypes were sown under controlled glasshouse conditions in 2016. Plants were grown at 22/16°C (day/night) temperatures. Pollen was collected for in vitro germination test. The samples were collected before anthesis and exposed to four different temperatures (20, 25, 30, 35°C). Heat-tolerant genotypes, such as FBA Ayla and PBA Nasma, had higher pollen germination rates at temperatures above 30°C. A higher rate of germinated pollen was linked to heat-tolerant genotypes under heat stress. Selected genotypes were tested further to understand whether plants exposed to mid-high temperatures 28/16ᵒC day/night in the vegetative phase can develop tolerance to high temperatures in later stages. The present data showed these plants were negatively affected and did not develop tolerance to heat stress in the later stages. From the findings of the current study, two faba bean genotypes (PBA Ayla and PBA Nasma) were identified as heat-tolerant genotypes to use in the breeding program. These data suggest that the impact of heat during flowering translates to pollen viability.